I really hope that I won't get penalized for posting here...
I think I have what the use of two other specials are.
Special 0x129 activates the roaming legends. It uses variable 0x4031 to determine which will roam. I tested this out by activating the special, and "faking" a battle with the legend using the wildbattle command. The icon then showed up on the World Map, indicating where it was.
I think Special 0x175 is used to calculate the amount of money dropped when you whiteout. In the whiteout script, Special 0x175 is called, and immediately following is the "player dropped $[buffer1]s" message. You mentioned how the Special 0x175 buffers a calculated value, so it seems like this is a likely reason for it. I could be wrong, though, since the amount of money lost is based on level of Pokemon and number of badges, not status.